1. Field of the Invention
The present invention relates to a fuzzy inference processing apparatus for performing fuzzy inferences.
2. Description of the Related Art
Many proposals concerning fuzzy inference processing apparatuses, such as fuzzy control apparatuses and fuzzy computers, have been conventionally made in a variety of literature.
For example, fuzzy inference processing apparatuses formed of an analog circuit are described in Published Unexamined Japanese Patent Application Nos. 2-93902, 2-93904, 2-93905, and 2-270030. Published Unexamined Japanese Patent Application No. 2-93902 discloses an analog fuzzy controller for outputting a fuzzy inference result by using signal lines in a number equal to the number of then-part membership functions to a deffuzification section in order to reduce the number of connector pins of the package when the controller is to be formed an IC. Published Unexamined Japanese Patent Application No. 2-93904 discloses a fuzzy control apparatus with an improvement responsibility of a closed loop control, i.e., a fuzzy control apparatus capable of following with a sufficient accuracy even target values changing with time, by obtaining a control signal using a fuzzy inference upon the change in the target signal. Published Unexamined Japanese Patent Application No. 2-93905 discloses a fuzzy control apparatus for performing control of a closed loop system with a short dead time and a small overshoot by determining the history of the control signal and correcting the control signal in accordance with the determination result. Published Unexamined Japanese Patent Application No. 2-270030 discloses a fuzzy processing apparatus capable of reducing the scale of circuits by performing multiplications, instead of minimum calculations between the grade of the if-part membership functions.
These fuzzy inference processing apparatuses disclosed in the above literature are formed of hardware so that they can perform high-speed inference calculations. However, these apparatuses are poor in flexibility and hence cannot easily correspond to changes in the fuzzy rule including changes in the number of input variables, the definition of the membership functions, and in the number of rules.
In order to overcome the above drawbacks, there is proposed a fuzzy inference processing apparatus that executes fuzzy inferences by software. In a fuzzy inference performed by software, however, if an inference mechanism is sophisticated or the number of data to be processed is large, the inference calculation speed undesirably becomes very low.
As described above, either of these two types of apparatuses has both advantages and disadvantages. In conventional fuzzy inference apparatuses, therefore, a system is constructed by one of software and hardware in accordance with the intended use, the object to be controlled, and the like. This gives rise to conflicting problems: if the inference speed of the system is increased, its flexibility is decreased; if the flexibility of the system is pursued, its inference speed is sacrificed.